Honda GX 690 Rev Issue

Long time since I have been on the forum. Have a Honda GX 690 with just under 1000 hours on it. Recently it started to rev a few times after I let go of the trigger then settled into idle. I have always changed oil every 50 hours and when this started I changed plugs, cleaned air filter and changed fuel filter. It stopped for a few hours but then came back. Starts just fine, runs fine, pressure is normal at the gun, etc just that when you take the load off the engine it does this revving before settling into idle. I have checked the throttle springs, arm, etc. Everything looks to be in place with nothing broken. Perhaps totally unrelated, but I did see a 3 inch flat bar that doesn’t connect to anything and appears to have no purpose by the throttle springs/arm. Any ideas fellas?

ill try to take a pic of the linkage of my 690 later for you. theres a vid on youtibe on how to set the carb gov. Maybe try it.

Update - I pulled a diagram off the web for the linkage and checked that all springs and cables are properly attached where they should be. All springs are in good shape and everything appears to move as it should. This picture shows the flat piece I was talking about - it was stuck into the throttle control level with the long side just resting on a cable holder not really doing anything - lever still moved freely. I took it out and it seems to be a forged aluminum piece that looks to have been broken on both ends as they are rough and uneven but I can not find where it came from -

I just spent ten minutes looking all over my machine and I didn’t see anything that even resembles that piece. Maybe a tool they use at the factory for assembly and they left it in yours? That’s my best guess.

never seen that either. Iooks like Allen key

In my retail days I don’t recall seeing any squared linkage rods like what you have pictured…they were all round. I agree with the others in stating that it looks like an allen key of sorts - a poor condition one btw.

Not an allen by any means. Just a forged aluminum flat piece of metal - after an exhaustive research appears to have nothing to do with the engine but strange it ended up in one on the holes of the throttle lever but again was just sitting there not doing anything. Didnt restrict movement of lever, just there.

Did it fix the problem?

Sounds like governor issues to me. I’ll bet that little thingy was serving a purpose when it was running right.

Sounds more like a sticky unloader to me. Sometimes they’ll hang up for a split second before it pops and releases the pressure. You can easily check this by hooking your peepers on the bypass hose in the tank and see if it’s letting water back to the tank when it does the revving thing. If it’s not, may be time for a new unloader.


Update - Checked on the unloader perspective. When I start up the machine, it starts perfectly and bypass immediately flows. When I check after using the machine in work for a bit and the revving or surging occurs, I see that the bypass is working perfectly. As soon as I let of the trigger the bypass is sending water to the buffer tank. I did this several times today to verify and confirm that every time I let go of the trigger the bypass would flow instantly. So it is safe to say the unloader is not the issue unless someone has info to probe this aspect further.

Some additional notes -

  1. It never occurs when I start up the machine. It always starts perfectly and runs fine.
  2. Seems like it takes awhile of being on the gun for it to start occurring. It is like only after it runs for awhile does it begin to occur.
  3. The first half of the day, I was too far away (Cleaning a baseball stadium) to actually hear the machine every time I let off the trigger. Later in the day when I could hear the machine, it was almost inconsistent. Some times when I let off, it would surge and other times it would not.

Keep the ideas coming fellas on what it might be? Will take some video tomorrow when I have hand helping me.


If the unloader is good and it sounds like it is, @TheWizard may be onto something with the governor issue. I know @Innocentbystander has experience R&R’ing those things so maybe he can chime in. Guy’s probably owned more Hondas than I’ve owned underwear.

It’s probably a coil. The governor is internal and is a solid half an afternoon to replace. I don’t try to fix much anymore unless it’s just a coil or the stupid fuse behind the key switch. With few exceptions, the 690’s last 3k hours with no problems and then it’s cheaper to just replace. Anything under that I swap with a new engine and fix the bad one in the winter.

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It’s get’n too much gas in it.

you may want to try a flow actuated unloader vs a trapped pressure unloader

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I haven’t seen you post in forever. Just wanted to pop in and say I love all you guys over at Kleen-Rite!

I’m using a flow unloaded and not a trapped.

Some additional info -

  1. The engine is not actually surging but hunting for idle when the load is taken off. It is actually decreasing RPM for a second then going back to idle RPM so it sounds like it is reving but really doing the opposite.
  2. I pulled the carb and cleaned it out. It was pretty clean to start, but since I had it off went ahead and clean it. The only this I found was the fuel intake on the carb has an insert filter that had some build up in it. After cleaning and reassembly, the engine still is hunting.

Throw that little screen away

i forgot to link it. If you feel you want to give it a shot, here it is.